Digital transport of data over distributed antenna network

ABSTRACT

A system for transporting data in a Distributed Antenna System (DAS) includes at least one Digital Access Unit (DAU) and a plurality of Digital Remote Units (DRUs) coupled to the at least one DAU. The plurality of DRUs are operable to transport signals between the plurality of DRUs and the at least one DAU. The at least one DAU includes: a data transport coder comprising: a framer, an encoder, a scrambler, and a serializer and a data transport decoder comprising: a deserializer, a decoder, a descrambler, a frame synchronizer, and a deframer.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/812,018 filed Nov. 14, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/574,071, filed on Dec. 17, 2014 and issued asU.S. Pat. No. 9,847,816 on Dec. 19, 2017; which claims priority to U.S.Provisional Patent Application No. 61/918,386, filed on Dec. 19, 2013.The aforementioned applications, and issued patent, are incorporatedherein by reference, in their entirety, for any purpose.

BACKGROUND OF THE INVENTION

Wireless and mobile network operators face the continuing challenge ofbuilding networks that effectively manage high data-traffic growthrates. Mobility and an increased level of multimedia content for endusers requires end-to-end network adaptations that support both newservices and the increased demand for broadband and flat-rate Internetaccess. One of the most difficult challenges faced by network operatorsis caused by the physical movement of subscribers from one location toanother, and particularly when wireless subscribers congregate in largenumbers at one location. A notable example is a business enterprisefacility during lunchtime, when a large number of wireless subscribersvisit a cafeteria location in the building. At that time, a large numberof subscribers have moved away from their offices and usual work areas.It's likely that during lunchtime there are many locations throughoutthe facility where there are very few subscribers. If the indoorwireless network resources were properly sized during the design processfor subscriber loading as it is during normal working hours whensubscribers are in their normal work areas, it is very likely that thelunchtime scenario will present some unexpected challenges with regardto available wireless capacity and data throughput.

To address these issues, Distributed Antenna Systems (DAS) have beendeveloped and deployed. Despite the progress made in DAS, there is aneed in the art for improved methods and systems related to DAS.

SUMMARY OF THE INVENTION

The present invention generally relates to communication systems usingcomplex modulation techniques. More specially, the present inventionrelates to distributed antenna systems that contain a microprocessor orother digital components, such as a Field Programmable Gate Array (FPGA)or Application Specific Integrated Circuit (ASIC). Timingsynchronization in a Distributed Antenna system is sensitive to the datacontent that is transported on the network. Cellular data is prone tolong periods of weak signals being present which can lead to long runsof zeros. A scrambler/descrambler is an effective technique to combatclock drift in a high data rate link. Embodiments of the presentinvention provide an efficient and effective method of insuring clocktiming synchronization in a remote unit to which data has beentransported over a digital link from a host unit to the remote unit.

Embodiments of the present invention provide systems and techniques thatare based on performing scrambling on the transmitted downlink data atthe Host unit and then descrambling on the received data at the remoteunit. Likewise, scrambling and descrambling are used for the transmitteduplink data being transported between the Remote and the Host unit.

According to an embodiment of the present invention, a system fortransporting data in a Distributed Antenna System (DAS) is provided. Thesystem includes at least one Digital Access Unit (DAU) and a pluralityof Digital Remote Units (DRUs) coupled to the at least one DAU. Theplurality of DRUs are operable to transport signals between theplurality of DRUs and the at least one DAU. The at least one DAUincludes: a data transport coder comprising: a framer, an encoder, ascrambler, and a serializer and a data transport decoder comprising: adeserializer, a decoder, a descrambler, a frame synchronizer, and adeframer.

According to a specific embodiment of the present invention, a systemfor transporting data in a Distributed Antenna System. The systemincludes a plurality of Digital Access Units (DAUs). The plurality ofDAUs are coupled and operable to route signals between the plurality ofDAUs. The system also includes a plurality of Digital Remote Units(DRUs) coupled to the plurality of DAUs and operable to transportsignals between the plurality of DRUs and the plurality of DAUs. Each ofthe plurality of DRUs includes: a data transport coder comprising: aframer, encoder, scrambler and serializer and a data transport decodercomprising: a deserializer, decoder, descrambler, frame synchronizer anddeframer; and a scheduler/dispatcher.

According to a particular embodiment of the present invention, a methodof providing serialized data is provided. The method includes receivingpayload I & Q data and receiving IP data. The method also includesframing the payload I & Q data and the IP data and encoding the frame.The method further includes scrambling the encoded frame to providescrambled data and serializing the scrambled data.

According to another particular embodiment of the present invention, amethod of transmitting RF data and IP data is provided. The methodincludes receiving the RF data at an RF port of a Digital Access Unit(DAU), receiving the IP data at an Ethernet port of the DAU, processingthe RF data to provide digital payload I & Q data, and framing thedigital payload I & Q data and the IP data to provide framed data. Themethod also includes encoding the framed data, scrambling the encodeddata, serializing the scrambled data, and transmitting the serializeddata through an optical fiber to a Digital Remote Unit (DRU). The methodfurther includes deserializing the serialized data, descrambling thedeserialized data, extracting frame synchronization for the descrambleddata, and decoding the descrambled data. The method additionallyincludes converting the decoded data to provide a representation of theRF data and the IP data, amplifying the representation of the RF dataand the IP data, and transmitting the amplified RF data and IP data froman antenna associated with the DRU.

According to a specific embodiment of the present invention, a systemfor transporting data in a Distributed Antenna System is provided. Thesystem includes a plurality of Digital Access Units (DAUs). Theplurality of DAUs are coupled and operable to route signals between theplurality of DAUs. The system also includes a plurality of DigitalRemote Units (DRUs) coupled to the plurality of DAUs and operable totransport signals between DRUs and DAUs, a data transport codercomprising: a framer, encoder, scrambler and serializer, and a datatransport decoder comprising: a deserializer, decoder, descrambler,frame synchronizer and deframer.

According to another specific embodiment of the present invention a,system for transporting data in a Distributed Antenna System isprovided. The system includes a plurality of Digital Access Units(DAUs). The plurality of DAUs are coupled and operable to route signalsbetween the plurality of DAUs. The system also includes a plurality ofDigital Remote Units (DRUs) coupled to the plurality of DAUs andoperable to transport signals between DRUs and DAUs, a data transportcoder comprising: a framer, encoder, scrambler and serializer. Thesystem also includes a data transport decoder comprising: adeserializer, decoder, descrambler, frame synchronizer and deframer. Thesystem further includes a scheduler and dispatcher.

According to yet another specific embodiment of the present invention, asystem for transporting data in a Distributed Antenna System includes aplurality of Digital Access Units (DAUs), wherein the plurality of DAUsare coupled and operable to route signals between the plurality of DAUs.The system also includes a plurality of Digital Remote Units (DRUs)coupled to the plurality of DAUs and operable to transport signalsbetween DRUs and DAUs and a plurality of Base Transceiver Stations(BTS). The system also includes a data transport coder comprising: aframer, encoder, scrambler and serializer, and a data transport decodercomprising: a deserializer, decoder, descrambler, frame synchronizer anddeframer.

Numerous benefits are achieved by way of the present invention overconventional techniques. For example, embodiments of the presentinvention provide improved clock timing synchronization utilized in thetransmission of cellular data. The present invention is applicable toany communication system that transports cellular data over a medium. Insome embodiments, a communication link is established between a localhost unit and a remote unit. A Field Programmable Gate Array (FPGA) orApplication Specific Integrated Circuit (ASIC) that incorporates aprocessor, such as a Power PC or Microblaze, can be used to control thedata flow to and from the Remote Unit. These and other embodiments ofthe invention along with many of its advantages and features aredescribed in more detail in conjunction with the text below and attachedfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a Distributed Antenna System (DAS),which includes one or more Digital Access Units (DAUs) and one or moreDigital Remote Units (DRUs).

FIG. 2 is a block diagram of a Digital Access Unit (DAU).

FIG. 3 is a block diagram of a Digital Remote Unit (DRU).

FIG. 4 shows the mapping of the data frame structure used to communicatebetween the DAU and the DRUs.

FIG. 5 is a block diagram of the coding structure at the Digital AccessUnit (DAU) downlink path and Digital Remote Unit (DRU) uplink path.

FIG. 6 is a block diagram of the coding structure at the Digital AccessUnit (DAU) uplink path and Digital Remote Unit (DRU) downlink path.

FIG. 7A is a block diagram of a scrambler for framed data according toan embodiment of the present invention.

FIG. 7B is a block diagram of a descrambler for framed data according toan embodiment of the present invention.

FIG. 8 is a simplified flowchart illustrating a method of providingserialized data according to an embodiment of the present invention.

FIG. 9 is a simplified flowchart illustrating a method of transmittingRF data and IP data according to an embodiment of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

A distributed antenna system (DAS) provides an efficient means ofutilization of base station resources. The base station or base stationsassociated with a DAS can be located in a central location and/orfacility commonly known as a base station hotel. The DAS networkcomprises one or more digital access units (DAUs) that function as theinterface between the base stations and the digital remote units (DRUs).The DAUs can be collocated with the base stations. The DRUs can be daisychained together and/or placed in a star configuration and providecoverage for a given geographical area. The DRUs are typically connectedwith the DAUs by employing a high-speed optical fiber link. Thisapproach facilitates transport of the RF signals from the base stationsto a remote location or area served by the DRUs.

An embodiment shown in FIG. 1 illustrates a basic DAS networkarchitecture according to an embodiment of the present invention andprovides an example of a data transport scenario between a BaseTransceiver Station 108, also referred to as a base station, andmultiple DRUs 101, 104, and 106. In this embodiment, the DRUs areconnected to the DAU 103 in a star configuration to achieve coverage ina specific geographical area.

FIG. 1 is a block diagram of one embodiment of a Distributed AntennaSystem which includes one or more Digital Access Units 103 and one ormore Digital Remote Units 101/104/106. The DAUs interface to one of moreBase Transceiver Stations (BTS) 108. Up to N DRUs can be utilized inconjunction with a DAU. The BTS 108 is coupled to the DAU by an RF cable109 suitable for carrying RF signals. In the embodiment illustrated inFIG. 1, the DAU is connected to the one or more DRUs using opticalfibers 102/105/107. In other embodiments that include more than one DAU,the DAUs can be coupled via Ethernet cable, Optical Fiber, MicrowaveLine of Sight Link, Wireless Link, Satellite Link, or the like. Althoughoptical fibers 102/105/107 are illustrated in FIG. 1, in otherembodiments, the one or more DAUs are coupled to the plurality of DRUsvia Ethernet cable, Microwave Line of Sight Link, Wireless Link,Satellite Link, or the like. Additional description related to DASarchitectures is provided in U.S. patent application Ser. No.13/211,243, filed on Aug. 16, 2011, now U.S. Pat. No. 8,682,338, thedisclosure of which is hereby incorporated by reference in its entiretyfor all purposes.

FIG. 2 is a block diagram showing a DAU system for base-stationapplications according to one embodiment of the present invention. TheDAU system 202 for the base-station applications has RF input and output203 that receives and transmits RF input/output signals and opticalinput and output ports illustrated by optical fibers 201A-201F.

The DAU system 202 includes four key components; an FPGA-based digitalcomponent 205, a down converter and up-converter component 204, analogto digital and digital to analog converter component 208, and an opticallaser and detector component 209. The FPGA-based digital component 205includes a field programmable gate array (FPGA), digital signalprocessing (DSP) units, Framers/De-Framers, andSerializers/De-Serializers. Additional description related to DAUs isprovided in U.S. patent application Ser. No. 12/767,669 (Attorney DocketNo. 91172-821440 (DW-1016US), filed on Apr. 4, 2010, Ser. No. 13/211,236(Attorney Docket No. 91172-821470 (DW-1022US), filed on Aug. 16, 2011,Ser. No. 13/211,247 (Attorney Docket No. 91172-821479 (DW-1024US), filedon Aug. 16, 2011, and Ser. No. 13/602,818, filed on Sep. 4, 2012(Attorney Docket No. 91172-850985 (DW-1025US), all of which are herebyincorporated by reference in their entirety for all purposes.

As illustrated in FIG. 2, the DAU 202 is a quad-band Digital Access Unit(i.e., operating at multiple bands, which can include transmit/receiveinput/output at the 700 MHz 203A, 900 MHz 203B, 1900 MHz 203C, AWS 203Dbands, although other bands are included within the scope of the presentinvention. The DAU can have an RF base station interface (typically tofour sectors) Although the DAU 202 illustrated in FIG. 2 includes thefour Tx/Rx RF ports described above, fewer or greater number of Tx/Rx RFports can be utilized. On the optical interface side (i.e., the rightside of FIG. 2), the DAU is connected to multiple remote radio units(RRUs), also referred to as digital remote units (RRUs) in a starconfiguration, a daisy chain configuration, or a combination thereofdepending on the particular network design. As illustrated in FIG. 2,six optical fiber interfaces 201A-201F are utilized in the illustratedembodiment.

Referring to FIG. 2, the downlink path RF signals entering the DAU atthe duplex RF input/output port 203A can be separated from uplinksignals by RF duplexer 230 and frequency-converted by down converter/upconverter 204, digitized by analog to digital converter 231, andconverted to baseband by digital processing function 232, which is partof the FPGA 205. Similar components are utilized for the other duplex RFinput/output ports as illustrated in FIG. 2. Data streams are then I/Qmapped and framed with monitoring and control signals in Framer/Deframer206. Specific parallel data streams are then independently converted toserial data streams in SerDes 207 and translated to optical signals bypluggable SFP optical transceiver modules 209, and delivered to opticalfibers 201A-201F. The six optical fibers deliver the serial optical datastreams to multiple RRUs. The other three sets of downlink RF pathsoperate similarly.

Referring to FIG. 2, following the description above, the uplink pathoptical signals received from the RRUs are received using optical fibers201A-201F, de-serialized by SerDes 207, deframed by Framer/Deframer 206,and digitally up-converted by digital processing function 232. Datastreams are then converted to analog IF by digital to analog converter233 and up-converted by upconverter UPC1, then amplified by RF amplifier234 and filtered by duplexer 230. The uplink RF signal enters the basestation at Uplink RF Port 203A. CPU 240 feeding Ethernet router 242provides separate Ethernet ports (REMOTE and AUX) for differentapplications.

FIG. 3 is a block diagram showing a Digital Remote Unit (DRU) systemaccording to one embodiment of the present invention. The DRU system 300has bidirectional optical signals carried on one or more of Fiber 1and/or Fiber 2 to communicate with the DAU illustrated in FIG. 2 andbidirectional RF port 320 operable to transmit and receive RF signalstransmitted and received by the RF antenna (Tx/Rx ANT). The DRU systemincludes four key components, described more fully below: an FPGA-baseddigital component 312, a down converter 313 and an up-converter 314,analog to digital (308) and digital to analog converter (309) (the grouplabeled as 321), an optical laser and detector component that includessmall form-factor pluggable (SFP) modules SFP1 and SFP2, and a poweramplifier component 318.

FIG. 3 illustrates a single-band Remote Radio Head Unit, also referredto as a digital remote unit, with one combined downlink/uplink antennaport 320. In other embodiments, multi-band DRUs are utilized, forexample, with downlink/uplink. antenna ports operating at 850 MHz, 1900MHz, and the like. Referring to FIG. 3, Fiber 1 connected to SFP1 301,is a high speed fiber cable that transports data between the (basestation and) host unit location and the Remote Radio Head Unit, Fiber 2can be used to daisy chain other remote radio head units, which arethereby interconnected to the base station or DAU. The software-defineddigital platform 312, which can be referred to as an FPGA, performsbaseband signal processing, typically in an FPGA or equivalent. The FPGAincludes Serializer/Deserializer 303. The deserializer portion extractsthe serial input bit stream from the optical fiber transceiver 301 andconverts it into a parallel bit stream. The serializer portion performsthe inverse operation for sending data from the Remote Radio Head Unitto the base station. In one embodiment, the two distinct bit streamscommunicate with the base stations using different optical wavelengthsover one fiber, although multiple fibers can be used in alternativearrangements. The DSP unit 304 includes a framer/deframer that deciphersthe structure of the incoming bit stream and sends the deframed data toa Crest Factor Reduction Algorithm module that is a component of the DSPunit 304. The Crest Factor Reduction Algorithm module reduces thePeak-to-Average Ratio of the incoming signal so as to improve the Poweramplifier DC-to-RF conversion efficiency. The waveform is then presentedto a Digital Predistorter block in the DSP 304. The digital predistortercompensates for the nonlinearities of the Power Amplifier 318 in anadaptive feedback loop. The downlink RF signal from the Power Amplifieris fed to duplexer 317 and is then routed to the antenna port 320.

Digital Upconverter 314 filters and digitally translates the deframedsignal to an IF frequency. Digital to analog converter 309 performs D-Aconversion and feeds an IF signal into upconverter 314. The Framer ofthe DSP unit 304 takes the data from the digital downconverter 305 andpacks it into a Frame for transmission to the BTS via the optical fibertransceiver 301. Analog to Digital converter 308 is used to translatethe analog RF uplink signal into digital signals. The receiver alsoincludes a downconverter 313.

Ethernet cable can be connected to gigabit Ethernet switch 310, which iscoupled to CPU 311 and is used to locally communicate with the DRU.

FIG. 4 shows an embodiment of the frame structure for the data that istransported between the DAU and DRUs. The data frame structure includesfive portions or elements; the SYNC portion 401, the Vendor specificinformation portion 402, the control and management (C&M) portion 403,the payload data portion 404, and the IP Data portion 405. The SYNCportion 401 is used at the receiver to synchronize the clock of thetransported data. The vendor specific information portion 402 isallocated for identifying the individual vendor information, which caninclude IP addresses associated with information and other informationthat can be specific to a particular vendor (e.g., a wireless carrier).The control and management portion 403 is used to monitor and controlthe remote units as well as perform software upgrades. Network controlinformation and performance monitoring along with control signals can betransmitted in the C&M portion 403. The payload I/Q data portion 404includes the cellular baseband data from the BTS 108 or from the RFantenna port 320. The IP data 405 is framed along with the payload I/Qdata for transmission between the DAU and the DRUs. The IP data caninclude IP traffic passing through the Ethernet router 242 or throughthe Ethernet switch 310. The framed data is eventuallyscrambled/descrambled as demonstrated in FIG. 5. The framing of the IPdata along with the cellular data enables both types of data to betransported through the system in either the upstream or downstreampaths.

FIG. 5 shows a block diagram of the coding structure of the transporteddata, including the payload I/Q data, from multiple inputs. FIG. 5illustrates how the portions of the data frame structure shown in FIG. 4are generated and illustrates how data can be coded for the DAU downlinkpath and the DRU uplink path. Accordingly, the processing illustrated inFIG. 5 occurs at the DAU for the Downlink path and at the DRU for theuplink path.

The scheduler and switch 508, Error Encoding 509, Sync 514, C&M 515 andVendor Specific Information 516 are provided as inputs to the Framer510. The payload data (i.e., the raw I & Q data) from multiple inputports (Payload I & Q data 501, 502, 503, 504, 505, and 506) as well asthe IP Network Traffic (Network IP traffic 507) are buffered anddelivered to the scheduler & switch 508. The scheduler & switch 508collates the buffered payload data from the various ports along with theIP Network traffic for the Framer 510. The scheduler utilizes analgorithm to ensure fairness amongst the ports and distribute theallocated resources. The scheduler also decides on which of the portsthe resources are allocated. As an example, IP Network data 507 can beallocated a lower priority in comparison to the payload data 501-506from the various ports.

The Error Encoder 509 performs a cyclic redundancy check encoding of thetransported data to insure that no errors occur during the datatransportation from the DAU to the DRU. The framed data is scrambledusing the scrambler 512 prior to being sent to serializer 513. One ofthe functions provided by the scrambler 512 is to remove long runs ofzeros and ones, for example, in the cellular data, so as to insure goodframe timing synchronization. This functions ameliorates issuespresented by the payload I & Q data, which includes the downlinkcellular data from multiple ports, which fluctuates with usage and canbe prone to long runs of zeros or ones. Thus, embodiments of the presentinvention integrate scrambling as part of the framing process to improvesystem performance, particularly frame synchronization. As illustratedin FIG. 4, framing of the data provides for separation of the payload I& Q data 404 and the IP data 405 as separate elements of the frame inorder to provide for separation of the two different types of data andthe attendant security that is provided through such a separation intoseparate elements. After framing and encoding, scrambling of the frameillustrated in FIG. 4 is performed to improve frame synchronization.

Referring to FIG. 2, the correspondence between the functional blocksillustrated in FIG. 5 and the modules of the FPGA 205 are as follows.Payload I & Q data 501-506 is provided as outputs of the DSPs 232, 252,254, and 256, The Network IP traffic 507 is provided as an output of theEthernet router 242. This data and traffic is processed by variousmodules of FPGA 205, including framer/deframer 206, which includesfunctions provided by scheduler and switch 508, scrambler 512, and thefunctional units therebetween, including error encoder 509, framer 510,and encoder 511. The serializer/deserializer modules (SerDes) 207 inFIG. 2 correspond to serializer 513 in FIG. 5. For purposes of clarity,the data flow from the DSPs 232, 252, 254, and 256 to theframer/deframer 206 and the SerDes 207 is not illustrated in FIG. 2, butwill be evident to one of skill in the art.

FIG. 6 shows the block diagram of the decoding structure of thetransported data. In FIG. 6, the decoding of data for the DAU in theuplink path and for the DRU in the downlink path is illustrated. The DAUreceives the uplink data from the remote units. The serialized data thenundergoes the following processing steps in the following modules:de-serializer 614, descrambler 612, frame synchronization 611, decoder613, deframer 610 followed by dispatching 608 the data to the variousoutput ports. The deframed data is decomposed into the C&M 615 data,Vendor information data 616, error check decoding 609 and the payload I& Q data. The dispatch 608 routes the scheduled payload data to thevarious ports. The descrambler performs the inverse operation to thescrambler 511.

Referring to FIG. 3, elements of the functionality illustrated in FIG. 6correspond to functionality provided by FPGA 312. Functionality,including that of the decoder 613, de-scrambler 612, frame synchronizer611, de-framer 610, error check 609, and dispatch 608 are performed bythe DSP 304 positioned between the SerDes 303/307 and the DDC 305/DIX,306 depending on whether the uplink or downlink path are utilized.

In relation to both FIGS. 2 and 5 and FIGS. 3 and 6, functionalityperformed by the various processing modules can be shifted to othermodules, as appropriate. For example, some or all of the functionalityof the framer/deframer 206 illustrated in FIG. 2 could be implemented bythe DSPs 232, 252, 254, and 256. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

FIG. 7A shows a block diagram of a scrambler 701 which represents thefollowing scrambling function: 1+X³⁹+X⁵⁸. The S # blocks 702/705 inFIGS. 7A and 7B are shift registers. FIG. 7B shows the correspondingdescrambler 704 for this scrambling function. Thescrambling/de-scrambling operation sums (i.e., binary addition) thereceived signal at summer 703 with a signal from 39 previous clockcycles and a signal from 58 previous clock cycles. Other specificnumbers of clock cycles other than 39 and 58 can be utilized accordingto embodiments of the present invention.

Cellular traffic load varies depending on the time of day, number ofactive users and many other factors. Inactive periods will result inweak signal strength for the various data payloads. These weak signalscan result in long runs of zeros for the payload data. This poses aproblem for high data rate transport of cellular signals. In particular,with long runs of zeros, it is very difficult to maintain framesynchronization at the receiver. The scrambler/descrambler is aneffective technique for mitigating these effects since it injects onesalong with the zeros in the data stream, which are then removed by thedescrambler at the receive side. Referring to FIGS. 4 and 5, the payloadI & Q data as well as the IP data is scrambled before being passed tothe serializer.

It should be appreciated that the specific processing steps illustratedin FIG. 5 and FIG. 6 provide a particular embodiment of the presentinvention. Other sequences of steps may also be performed according toalternative embodiments. For example, alternative embodiments of thepresent invention may perform the steps outlined above in a differentorder. Furthermore, additional steps may be added or removed dependingon the particular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

FIG. 8 is a simplified flowchart illustrating a method of providingserialized data according to an embodiment of the present invention. Themethod includes receiving payload I & Q data (810) and receiving IP data(812). The payload I & Q data can be computed based on RF cellulartraffic received at either a DAU or a DRU. The method also includesframing the payload I & Q data and the IP data (814) and encoding theframe (816). The framing of the payload I & Q data and the IP data,which can be independent of each other, can utilize independent elementsof the frame to maintain the different kinds of data in differentregions of the frame to provide for security and other benefits. Themethod further includes scrambling the encoded frame to providescrambled data (818) and serializing the scrambled data (820).

In a particular embodiment, the method also includes receiving theserialized data, for example at a DRU, deserializing the serializeddata; descrambling the deserialized data, determining framesynchronization information, and decoding the descrambled data. Themethod further includes deframing the synchronized and decoded data.Accordingly, the method can include providing the payload I & Q data andthe IP data, which can be dispatched as illustrated in FIG. 6.

It should be appreciated that the specific steps illustrated in FIG. 8provide a particular method of providing serialized data according to anembodiment of the present invention. Other sequences of steps may alsobe performed according to alternative embodiments. For example,alternative embodiments of the present invention may perform the stepsoutlined above in a different order. Moreover, the individual stepsillustrated in FIG. 8 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

FIG. 9 is a simplified flowchart illustrating a method of transmittingRF data and IP data according to an embodiment of the present invention.The method includes receiving the RF data at an RF port of a DigitalAccess Unit (DAU) (910), receiving the IP data at an Ethernet port ofthe DAU (912), and processing the RF data to provide digital payload I &Q data (914). The RF data can include analog RF data, cellular data, orthe like. The IP data can be independent from the RF data. The methodalso includes framing the digital payload I & Q data and the IP data toprovide framed data (916), encoding the framed data (918), scramblingthe encoded data (920), serializing the scrambled data (922), andtransmitting the serialized data through an optical fiber to a DigitalRemote Unit (DRU) (924). As illustrated in FIG. 4, the payload I & Qdata and the IP data are framed as separate elements of the framed datain some embodiments.

At the DRU, the method includes deserializing the serialized data (926),descrambling the deserialized data (928), and decoding the descrambleddata (930). In some embodiments, frame synchronization information isextracted (932) prior to decoding of the descrambled data (930) asillustrated in FIG. 6. In other embodiments, the method further includesextracting frame synchronization for the decoded data (932), convertingthe decoded data to provide a representation of the RF data and the IPdata (934), amplifying the representation of the RF data and the IP data(936), and transmitting the amplified RF data and IP data from anantenna associated with the DRU. Referring to FIG. 3, conversion of thedecoded data can include a digital to analog conversion process asillustrated by DAC 309 and upconversion by upconverter 314.

It should be appreciated that the specific steps illustrated in FIG. 9provide a particular method of transmitting RF data and IP dataaccording to an embodiment of the present invention. Other sequences ofsteps may also be performed according to alternative embodiments. Forexample, alternative embodiments of the present invention may performthe steps outlined above in a different order. Moreover, the individualsteps illustrated in FIG. 9 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

Appendix I is a glossary of terms used herein, including acronyms.

APPENDIX I Glossary of Terms

-   ACLR Adjacent Channel Leakage Ratio-   ACPR Adjacent Channel Power Ratio-   ADC Analog to Digital Converter-   AQDM Analog Quadrature Demodulator-   AQM Analog Quadrature Modulator-   AQDMC Analog Quadrature Demodulator Corrector-   AQMC Analog Quadrature Modulator Corrector-   BPF Bandpass Filter-   CDMA Code Division Multiple Access-   CFR Crest Factor Reduction-   DAC Digital to Analog Converter-   DET Detector-   DHMPA Digital Hybrid Mode Power Amplifier-   DDC Digital Down Converter-   DNC Down Converter-   DPA Doherty Power Amplifier-   DQDM Digital Quadrature Demodulator-   DQM Digital Quadrature Modulator-   DSP Digital Signal Processing-   DUC Digital Up Converter-   EER Envelope Elimination and Restoration-   EF Envelope Following-   ET Envelope Tracking-   EVM Error Vector Magnitude-   FFLPA Feedforward Linear Power Amplifier-   FIR Finite Impulse Response-   FPGA Field-Programmable Gate Array-   GSM Global System for Mobile communications-   I-Q In-phase/Quadrature-   IF Intermediate Frequency-   LINC Linear Amplification using Nonlinear Components-   LO Local Oscillator-   LPF Low Pass Filter-   MCPA Multi-Carrier Power Amplifier-   MDC NIBS Multi-Directional Search-   OFDM Orthogonal Frequency Division Multiplexing-   PA Power Amplifier-   PAPR Peak-to-Average Power Ratio-   PD Digital Baseband Predistortion-   PLL Phase Locked Loop-   QAM Quadrature Amplitude Modulation-   QPSK Quadrature Phase Shift Keying-   RF Radio Frequency-   RRH Remote Radio Head-   RRU Remote Radio Head Unit-   SAW Surface Acoustic Wave Filter-   UMTS Universal Mobile Telecommunications System-   UPC Up Converter-   WCDMA Wideband Code Division Multiple Access-   WLAN Wireless Local Area Network

What is claimed is:
 1. A system for transporting data in a DistributedAntenna System, the system comprising: at least one Digital Access Unit(DAU); a plurality of Digital Remote Units (DRUs) coupled to the atleast one DAU, wherein the plurality of DRUs are operable to transportsignals between the plurality of DRUs and the at least one DAU; whereinthe at least one DAU includes: a data transport coder comprising: aframer, an encoder, a scrambler, and a serializer; and a data transportdecoder comprising: a deserializer, a decoder, a descrambler, a framesynchronizer, and a deframer.